This invention relates to urethral catheters and more specifically to systems and methods for anchoring such catheters in urethras.
An example of a urethral catheter of the type to which this invention relates is a catheter disclosed in U.S. Pat. No. 4,350,161 to Richard C. Davis, Jr. In the catheter disclosed in that patent there is a valve which, when the catheter is properly anchored in the patient's urethra, can be activated by application of an external force. That catheter is designed so that when it is installed its downstream tip does not extend beyond a penile meatus in any patient position. As is set forth in U.S. Pat. No. 4,350,161 of Richard C. Davis, Jr., a method of inserting such an indwelling urethral catheter includes the step of determining the length of the patient's urethral tract. Thus, since the advent of the indwelling urethral catheter of the type described above, proper sizing of the catheter has been appreciated as a critical element in a protocol for positioning the device and in its proper functioning.
During development of this catheter it has come to be better appreciated that as the bladder fills and empties and the body moves, the bladder and urethra shift and stretch relative to one another. It has been determined that overall urethral length is generally shortest when a patient is lying down and lengthens when the patient is sitting or standing. Thus, it has been determined that a properly sized male indwelling urethral catheter of this type must be short enough to remain totally inside the patient's urethra in all positions, but yet long enough to allow easy access the valve located in the patient's urethra for voiding and for removal of the catheter itself.
If it is sized too long, the catheter may occasionally protrude from the tip of the penis, potentially causing pain, swelling, and infection. If the catheter is too short, the patient may not be able to easily access the valve to properly actuate it. Further, the patient may have difficulty removing the catheter.
Another feature of the indwelling urethral catheter described in U.S. Pat. No. 4,350,161 to Richard C. Davis, Jr. is that it includes not only a bladder balloon but also an anchoring urethral cuff balloon along a catheter drainage shaft for inflating in the patient's urethra. A primary purpose of the urethral anchoring cuff balloon, as was described in U.S. Pat. No. 4,350,161, is to prevent retrograde movement of the catheter into the bladder by using the prostatic urethra as a buttress against which the urethral anchoring cuff balloon is juxtaposed.
To meet different lengths of normal adult urethral tracts, indwelling urethral catheters of the type of this invention, have been, to date, manufactured in six different overall lengths so that most any length of an adult male penis and urethral tract can be accommodated. However, notwithstanding this, sizing problems have continued to be encountered. In this regard, until recently, an indwelling urethral catheter of the type of this invention was fitted to a patient by first placing a measuring catheter, having a bladder balloon and drainage shaft extending beyond the patient's penile meatus, in the patient. By noting the position of the penile meatus along the measuring catheter's drainage shaft, with the patient in various positions, the overall length of the patient's urethral tract was determined. An indwelling urethral catheter was then chosen from the six different lengths corresponding to the overall length of the patient's urethral tract. Using this method, however, problems have continually been encountered in choosing the proper length catheters. That is, after catheters, whose lengths were determined as described above, have been installed it has been found that they often have not remained in their preferred positions. As the body accommodates to the presence of the device in some cases they have shifted downstream to extend beyond a patient's penile meatus when the patient was in a lying position and in other cases they have shifted upstream so far from the meatus that the patient has not been able to activate the valve to urinate. Because of this, it has sometimes been necessary to try various size catheters in a patient, one after the other--even though the patient was previously measured--until a catheter of the correct size, if ever, was found. Thus, in many cases, catheter sizes have actually been determined as much by trial and error as by measuring, if at all. Such trial and error has resulted in discomfort for patients and has proven to be expensive, since it has resulted in the expenditure of many catheters and much time and effort; and often patients were not able to be fitted at all.
The problem has been that some inserted prior-art indwelling urethral catheters, of the type of this invention, have experienced undue relative linear movement along urethral tracts. That is, sometimes they have appeared to be in their correct positions but then at other times they have moved linearly, within the urethral tract, to inappropriate positions. Thus, when some catheters were initially sized using the above-described method, which relied solely on the bladder-to-meatus length, they were occasionally noted to shift downstream in the urethra; thereby appearing to be "too long", and their tips intermittently protruded from the penile meatus. It has been assumed that such shifting represented "device failure"; presumably the bladder balloon had leaked thus allowing downstream migration. An opposite situation has been noted in some patients who at first could easily access their valves but who, over time, had increasing difficulty accessing their valves because their catheters migrated upstream. Again, this was previously interpreted as a "device failure" whereby the urethral anchoring cuff balloon was thought to have deflated allowing such upstream migration.
It has now been realized that the distance between the bladder neck orifice and the bulbous urethra, which shall be referenced herein as the "interballoon urethral segment length" and as the "prostatic urethral length", varies tremendously among patients. Such a difference in interballoon urethral segment lengths is illustrated in FIG. 3 where are shown diagrammatically: a patient's bladder 10, the patient's penis 12, and a urethral sizing catheter 14 extending through a urethral tract 16 from the bladder 10 to beyond a penile meatus 18. For purposes of illustration, three different size interballoon urethral segment lengths (i.e. prostate gland or prostate Fossa as the case may be) are represented diagrammatically on FIG. 3. It should be understood that individual patients will have only one of these interballoon urethral segment lengths; however, all three are depicted on FIG. 3 so that a reader can compare the different size interballoon urethral segment lengths with interballoon spacings (balloon spacings).
A normal-size prostate gland 20 has a downstream side 22 which is located approximately four centimeters from the interior surface of a bladder neck orifice 10a (or downstream side 24 of a bladder balloon 26). This four centimeter spacing is represented by the letter "b" in FIG. 3. However, an enlarged, or hypertrophic prostate gland 28 has a downstream side 30 which is spaced approximately 5.5 cm from the downstream side 24 of the bladder balloon 26 in the bladder 10. This 5.5 cm measurement is signified by the letter "a" in FIG. 3. Finally, a post prostatectomy prostatic Fossa 32, which is essentially what is left when a prostate is removed (or at least diminished), has a downstream side 34 which is spaced approximately 2.0 cm from the downstream side 24 of the bladder balloon 26 when it is in the bladder 10. This downstream side of the bladder balloon 26 can also be influenced to some extent by the position of a bulbous urethra 68. In this regard, when a patient's prostate is removed, it sometimes happens that some of the bladder must also be removed and reconstructed. In this process, these elements move relative to one another to some extent.
In any event, this 2.0 cm measurement is indicated by the letter "c" in FIG. 3. It should be understood that these measurements are only given as approximations and that they can vary significantly from patient to patient. However, it can be seen from these approximations, in FIG. 3, that the relative interballoon urethral segment lengths ("b", "a", and "c") of patients--and thus necessary catheter balloon spacings--can vary by a factor of nearly three (comparing "a" with "c").
It has been suggested that both urethral sizing catheters and indwelling urethral catheters be manufactured in sets, with the catheters of each set having approximately the same length, but each catheter of the set having different balloon spacings to accommodate the different interballoon urethral segment lengths (a, b, c). Under this system, it has been anticipated that up to 18 different indwelling urethral catheter sizes will be necessary, with there being six different overall clinical catheter lengths, but at least three different balloon spacings for each overall clinical catheter length. Further, it is anticipated that at least three urethral sizing catheters will be necessary.
Although the system of these many different catheters solves the problem of the various interballoon urethral segment lengths, it is expensive to manufacture so many different-size catheters.
Thus, it is an object of this invention to provide an anchoring system for an indwelling urethral catheter and, possibly for a urethral sizing catheter, which accommodates various interballoon urethral segment lengths so that a single catheter can be used with various interballoon urethral segment lengths.
Similarly, it is an object of this invention to provide a method of anchoring a urethral catheter which accommodates substantial differences in urethral anatomies.